Electric signaling system



June 28, 1938. T. A. LUNDELL 2,122,102

ELECTRIC SIGNALING SYSTEM Filed Feb. 27, 1956 2 Sheets-Sheet 1 Fig. 2

June 28, 1932. T, Ar, LUNDELL' 2,122,102

ELECTRIC SIGNALING SYSTEM Filed Feb. 27, 1936 2 Sheets-Sheet 2 Patented June 28, 1938 UNITED STATES ELECTRIC SIGNALING SYSTEM 'Torsten Adil Lundell, Appelvlken, Sweden Application February 27, 1936, Serial No. 66,135 In Sweden March 2, 1935 8 Claims. (Cl. 179-2752) The present invention relates to electric signaling systems. More particularly the invention relates to electric signaling systems of the kind in which a certain one of a plurality of senders shall '.be automatically put into electric connection with a certain one of a plurality of receivers. The invention .has for its object to provide improved arrangements for establishing the connection.

It has been previously proposed to use as a substitute for-mechanical selectors in the establishing of .such a connection a selector the wiper of which consists of a ray of light. This arrangement is, however, expensive both as regards costs of installation and operation since the ray of light must be modulated in order to be able to transmit speaking currents. actuate from a sender by means of a directable ray of energy a definite one of a. plurality of re-, ceivers whereby connection between sender and receiver is established. This principle is in certain cases advantageous but has not hitherto been realized in an embodiment capable of competing with mechanical selectors. According to the present invention the signaling system comprises controllable electron or discharge paths by the aid of which the desired connection is established and maintained. The invention renders possible the provision of some very simple and reliable arrangements.

The invention will now be described more closely with reference to the accompanying, drawings showing arrangements which can be employed in various kinds of signaling systems but which for the purpose of explaining their operation have in certain cases been described as forming parts of an automatic telephone system. In the drawings,

Figure 1 shows in principle the use of a cathode ray tube in a system comprising finders, cord circuits and final selectors;

Figure 2 shows an example of the employment of a tube having two beams of cathode rays;

Figure 3 illustrates a two-wire connection over cathode ray tubes;

Figures 4, 5, and-6 show an example of a tube for use in a system according to the invention in which tube a beam of cathode rays ignites a discharge path between contacts connected to the sender and to the receiver;

Figure 7 illustrates an example of an arrangement in which the charging of a grid by the thermionic ray causes a discharge between cathode and anode in a thyratron type tube and thus a connection between a cord circuit and a subscriber.

In Figure 1 is shown a signaling system, for; instance, a telephone plant in which two cathode Furthermore, it is known to manner. A voltage applied between the cathode and an anode in the tube (not shown) accelerates and concentrates the thermionic current from the cathode in knownmanner so. that part of the currentcontinues past the anode and strikes on the wall V. The beam of electron rays can be controlled laterally and in elevation in a manner known per se by means of deflector plates or magnets. The contacts of Ks are connected with senders Si-Sl and the contactsof Ks are connected with receivers Nit-Ml. When a sender S1 desires communication with a receiver M4 there is at S1 applied a voltage to the line which voltage characterizes the contact in Ks with which S1 is connected. Means can also be provided for letting the same voltage cause a searching movement of the cathode ray in Ks which movement can be continuous, if desired, the cathode ray then sweeping over the contacts as in a mechanical finder employed in automatic telephone systems. The ray controlling arrangements are so devised that, as soon as the ray is directed towards the contact marked with the particular potential, they bring the ray to stop. The calling sender becomes in this manner connected with the cord circuit SN. Impulses from S1 now actuate deflector plates in Kv so that the ray in said tube is directed towards the contact in Ki) with which the desired receiver is connected whereby the desired connection between S1 and M4 is established.

Figure 2 illustrates the principle of a connection in whichtwo rays having dififerent functions are produced in a common cathode ray tube Kd. One of the rays is arranged as a finder traversing the contacts whereas the other ray is arranged as a selector. The subscribers stations A1-A4 which act both as senders and as receivers can thus be connected together similarly as in a connection according to Figure 1 with multipled sender and receiver circuits. If, for instance, As

is to be connected with As the finder ray is setv on the contact corresponding to- A: whereafter the selector ray is set by means of selector inipulses transmitted from As on the contact corresponding to A3.

In the schematic drawings described above the lines have been shown as single wire lines and a return has been provided through the indicated earthing of the sender and of the receiver. In practical embodimentsthe lines are usually made as two-wire lines and are as in ordinary automatic telephone systems brought to the selector arrangements in multiple.

In the connection according to Figure 3 there is shown in principle an example of how a twowire connection can be established according to the invention. The two tubes K and K respectively included in each of the line branches are in this case arranged as finders. A contact "in 3 attains the screen of one of the tubes is over the secondary winding of a transformer Ti connected with the corresponding contact of the other tube, the primary winding of the transformer being connected to thesender S. In corresponding man ner the cathodes are mutually connected over one winding of a transformer T2 the other winding of which is connected to a receiver M. The

midpoints of the windings connected. to the tubes are connected together. The part of the line containing the cathode ray tubes .is thus.connected to the two other parts of the line through the transformer. It is hereby rendered possible to transform to a highervalue the characteristic impedance for the part of the line containing the tubes and to connect the direct current circuits of the tubes across the midpoints of the transformers without influencing the signaling circuit. A transformation of the characteristic impedance is generally necessary since the resistance in the cathode rays is rather great even when evacuated special tubes are employed.

In the above described connection the cathode ray is used in the same manner as a wiper in mechanical selectors and finders so thatior instance in the transmission of speech the speaking currents flow over the cathode ray. However, there are also other possibilities according to the invention.. In Figures 4 and 5 a tube is shown by means of which a connection is established in such a manner that the cathode ray causes a discharge between two contacts in a discharge path between which the connection is established, the ray thus bringing about the connection without forming part thereof. The tube shown in Figure 4 in longitudinal section is intended to be used in connection with cord circuits. The tube is by means of a wall V divided intotwo chambers one of which contains the cathode and is evacuated as an ordinary cathode ray tube and the other one of which is gas filled as in a glow discharge lamp. In the wall V which for example can consist of glass there are provided windows]? which let through the cathode ray, the windows consisting for instance of thin metal foils. In the gas filled chamber there are arranged two contact groups SNI. E1 and 8N2, E2. One of the contact groups consists on the one hand 01' a metal net (or a perforated metal Plate) 8N1 connected to one branch of the cord circuit and on the otherhand of contacts Ei provided with apertures and connected each to one of the two conductors in a plurality of subscribers lines. The second contact roup 'consists in similar manner of a. net or the like SN: connected to the other conductor of the cord circuit and of contacts E2 each connected to the second conductors in the subscribers lines. Figure 5 shows the contacts E1 arran ed on a plate of insulating material. The windows in the wall V and the holes in the nets SN1 and SN: and in the contacts E1 and E2 are so ositioned behind each other that the cathode ray can pass through the same. When the tube is connected as a finder, selector-or the like. there is applied such a voltage between SN1 and E1 and between SN: and E; that as soon as the cathode ray is directed through a window F and passes the contacts a discharge takes .place between 8N1 respectively SN: and that. contact V1 respectively V3 through the hole of which the ray passes. Through this discharge the res ective contact E1 is connected with SN1 and the respective contact E: withSNz. The distance between E1 and 8N1 and between E: and SN: should be small as compared with the distance between different E1 or E1 contacts in' order that the discharge shall not spread from one discharge path to an adjacent one. Walls of insulating material between the diflerent contacts can also be pro- 5 vided for protecting against such a spreading of the discharge.

- If the. cathode ray tube according to Figures 4 and 5 is used as a finder, for example in an automatic telephone system, only those contacts E1, 1 E: which correspond to the calling subscriber are given through the call the voltage in rela tion to SN1 or SN: respectivelyrequired for initiating a discharge, the two paths under tension being ignited as soon as the ray performing a 15 searching movement over the contact rows reaches the contacts in question. If, on the other hand, the tube is to be used as a selector the ray is moved by means of selector impulses so that it is directed through the desired contacts and causes discharge between them. Preferably the rayis normally extinguished and the voltages on the deflector plates controlling the direction of the ray supplied to the deflector plates before the ray is lighted. The ray is thereafter lighted for a moment and causes the desired discharge. The ray can thereafter be used to bring about other connections. This can be the case for instance in a contact construction according to Figure 6 where the contacts for six cord circuits SN con- .30 sist of horizontal metal bands, as shown on the drawings, the two conductors ofeach cord circuit being connected with two metal bands positioned behind each other in analogy with SNI and SN:

in Figure 4. The correspondence to the contacts .35 E1, E: consists of vertical metal bands, and two bands positioned behind each other can be said to correspond to a row of contacts E1 and a row of contacts E: respectively. To each such pair of bands is connected a subscribers line. In said 4,0 construction a multiple is obtained in the tube" ting the ray bring about a connection between two contacts by igniting a controllable electron path. In this case mutually insulated contacts EL are arranged on the screen K of the tube. To each such contact are connected two grids'in a tube TY of thyratrone type, one grid forming part of a group of electrodes the cathodes of which are connected with one of the cord circuits, and the other grid being included in a corresponding manner in a. group in which the cathodes are connected to the other conductor in the cord circult. To two mutually connected grids correspond two" anodes connected with a subscriber A1-A-1. In connection with Figure there is also shown an example of a connection for controlling the thermionic ray by means of impulses. Across the g0 deflector plates SP is connected a condenser C1. The condenser is connected with one of its plates to the positive terminal of a source of current and can be connected with its other plate over a normally open relay contact I to the negativecs terminal of the source of current. A condenser C2, which is small as compared with the condenser 01, can be shunted to the last mentioned condenser in series with a resistance R by means of a relay contact 2 which in its position of rest,7 0

short circuits the condenser and the resistance.

By closing the contact I for a moment and thereafter permitting it to gov back to its position of rest the condenser C1 and the deflector plate SP are charged to a voltage which brings the.

cathode ray back. to its original position. If thereafter the contact 2 is actuated, for instance .by an incoming selector impulse, so that it octacts. Between every impulse the condenser 02' discharges over the contact 2 in the right hand' position of the latter. According as the voltage across C1 falls due to the discharges over C2 the change in voltage for each impulse decreases and consideration mustbe given to this condition in dimensioning the elements included in the arrangement.

A cathode ray can also be used according to-the invention to initiate and control in other manner a discharge between the contacts to..be connected together. .As is well known a circuit subj-ected to thermionic radiation emits secondary electrons. This phenomenon can be utilized according to the invention in such manner that the cathode ray is directed towards one of the contacts while, the other contact is so positioned that the secondary emission will strike thereon. Through a suitable selection of the material of the first mentioned contact and through a suitable mutual positioning and a. proper shaping of the two contacts it is possible to cause the current of secondary electrons to become so strong that a satisfactory connection between the contacts is produced.

The electron path by the aid of which the connection is established, for instance according to the principle illustrated in Figures 1 to 3, can be designed in a plurality of diflerent ways. Thus the thermionic tube can be provided with a grid which after the thermionic ray has been directed to the desired contact controls theintensity of the current as in an ordinary three electrode tube, one subscriber being connected with the grid and the cathodev and the other with its contact acting as an anode and the cathode. In this construction it is possible through an amplifying action to compensate for the damping which for example according to the construction shown in Figure 3 is caused by the high resistance of the ray.. An. inconvenience in said arrangement is, however, that it can be designed only for one direction of speech wherefore it is necessary in using the same to provide a similar selector (or finder respectively) for the other speaking direction in analogy with the two ampliiiers in a two-wire repeater.

I claim:-'

1. In a communicating system in combination a number of conductors, a discharge tube, a set of electrodes in said tube, said electrodes being connected each to one ofv said conductors, means for producing a cathode ray in said tube, means for directing said ray 'in different directions against the. set of electrodes, and means for selecting one of said directions and for fixing the direction or the ray in the selected position so as to establish electric connection between diflerent electrodes, said electrodes being connected with control grids in discharge paths of thyratrone type in such a manner that upon irradiation of an element the resistance of the thyratrone' discharge paths controlled through the corresponding grid dropsv from a very high value to a low value, senders and receivers connected to said thyratrone discharge paths being then connected with each other.

2. In a communicating system in combination a number of conductors, a discharge tube, a set of electrodes in said tube, said electrodes being connected each to one of said conductors, means for producing a cathode ray in said tube, means for deflecting said ray in difierent directions so as to cause scanning movement of the ray' over said set of electrodes and means under the control of potentials on said electrodes for stopping said scanning movement in a selected position of the ray so as to establish electric connection be-' tween difierent electrodes.

3, In a communicating system in combination a number of conductors, a discharge tube, a set of electrodes in said tube, said electrodes being connected each to one of said conductors, means for producing a cathode ray in said tube, means for directing said ray in different directions, and means for producing discharge between difierent electrodes under the influence of said ray so as to establish electric connection between said electrodes.

4. In a communicating system in combination a number, of conductors, a discharge tube, a set of electrodes in said tube, said electrodes being connected each to one of said conductors, means for producing a cathode ray in said tube, means for directing said ray in different directions and means for producing glow discharge between difieren't electrodes under the influence of said ray so as to establish electric connection between said electrodes.

5. In a communicating system in combination,

a discharge tube, a cathode, sets of apertured I electrodes arranged in different transversal planes in said tube, each electrode being disposed in longitudinal alignment with one electrode of each of the other sets; a number of conductors connected to the electrodes in said sets 'of electrodes, means for producing a cathode ray in said tube, and means for directing said ray selectively against the apertures of the electrodes so as to establish electric connection between electrodes of different sets.

' 6. In a communicating system in combination, a discharge tube, a set of apertured electrodes in said tube, a second set of electrodes disposed each behind one of said apertured electrodes, a number of conductors connected to the electrodes in said sets of electrodes, means for producing a cathode ray in said tube, and means for directing said ray selectively against the apertures of the electrodes of said first set so as to establish electric connection between an electrode of the first set and the appertaining electrode of the second set.

I. In acommunicating system in combination a discharge tube, a set of electrodes within said tuba-means for producing a cathode ray in said tube, means for directing said ray in different directions, and means for producing discharge between difierent electrodes under the influence of said ray, a number of said electrodes being connected in common with, a cord circuit and other of said electrodes being connected each with a telephone subscriber's line.

8. A system according to claim 5, characterized in that a number of said electrodes are mutually. 

